Bump cdav-library from `a9642c7` to `79dee27`

Bumps [cdav-library](https://github.com/nextcloud/cdav-library) from `a9642c7` to `79dee27`.
- [Release notes](https://github.com/nextcloud/cdav-library/releases)
- [Commits](https://github.com/nextcloud/cdav-library/compare/a9642c7c83db37120f8c74306c7e761f3e78524d...79dee27bc92bf3b6ece57fb6097d602ce574612a

)

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